The World Health Organization (WHO) today declared that the Ebola outbreak in Liberia is over, marking the first time since the outbreak began 2 years ago that all three affected West African countries have been free of the virus at the same time.

The WHO's acknowledgment of today's achievement came with words of caution that new flare-ups are likely to occur in the months ahead. Liberia is an example of that challenge, having gotten cases to zero twice before, only to have the disease spark again—both instances likely caused by lingering virus in survivors.

In a briefing before the United Nations General Assembly in New York City yesterday, WHO Director-General Margaret Chan, MD, MPH, said the outbreak disrupted all aspects of life in the three affected countries but showed the power of international solidarity. She added that the next 3 months are critical, with ongoing efforts needed to boost national health systems and maintain close vigilance.

"Recovery will take some time. While the job is by no means finished, no one anticipates that the situation will return to what we were seeing 15 months ago," Chan said.

Liberia now enters a 90-day period of enhanced surveillance.

Managing reintroduction risks

In a statement today, the WHO said 10 reintroductions of Ebola have occurred. Though survivors clear the virus from their bloodstreams relatively quickly, it can persist longer in immune-protected areas. For example, the WHO said the Ebola virus can remain in the semen of a small number of male survivors for as long as 1 year, and in rare instances, be transmitted to sexual partners.

Bruce Aylward, MD, MPH, the WHO's assistant director-general in charge of Ebola outbreak response, said the risk of flare-ups is diminishing as the virus gradually fades from the survivor population. "A massive effort is under way to ensure robust prevention, surveillance and response capacity across all three countries by the end of March," he said.

The WHO added that it is working with country governments to ensure that survivors have access to medical and psychosocial care, as well as screening for persistent virus.

Liberia now enters a 90-day period of enhanced surveillance.

In its latest numbers released yesterday, the WHO said 28,601 confirmed, probable, and suspected cases were reported in West Africa's outbreak countries, 11,300 of them fatal. Sierra Leone tallied the highest number of cases, though Liberia had the most deaths.

Reactions mark occasion

Groups and individuals affected by the outbreak today weighed in on the landmark reached by Liberia and the outbreak countries as a whole, widely seen as the end of the outbreak.

Doctors without Borders (MSF), the first aid group to arrive on the scene and play an instrumental role in warning the world about the emerging outbreak, called on the global community to draw on the lessons learned in the Ebola outbreak to better prepare for future outbreaks. MSF is continuing its work in the three countries by running survivor-support clinics.

Joanne Liu, MD, MSF's international president, said "Today is a day of celebration and relief that this outbreak is finally over." She added, however, that the response wasn't limited by a lack of means, but by a lack of political will to rapidly respond. "The needs of patients and affected communities must remain at the heart of any response and outweigh political interests."

Partners in Health (PIH), an aid group that saw some of its health workers sickened in the outbreak, said on its Twitter stream today that its thoughts were with the Ebola survivors and that as it celebrated the outbreak's end, it was committed to strengthening health systems in Sierra Leone and Liberia.

Ada Igonoh, MD, a Nigerian doctor who survived an Ebola infection in August 2014 and delivered a healthy baby girl at a California hospital last November, tweeted, "RIP to the thousands we lost during the Ebola outbreak. Gone but not forgotten.

She added: "It is my hope and prayer that West African and the world learn from the Ebola outbreak that consumed thousands. May we do better next time."